1. Field of the Invention
The present invention relates to an expansion wedge for use with a heat exchanger tube which expands the diameter of an opening of a flat tube to be inserted into a tube hole formed in a header member and which brings the opening into close contact with the tube hole, as well as a structure for mounting a tube to a header member of the heat exchanger manufactured through use of the expansion wedge.
The present application is based on Japanese Patent Applications No. Hei. 11-44875 and 2000-23925, which are incorporated herein by reference.
2. Description of the Related Art
According to a known method of manufacturing a heat exchanger, such as a radiator, an opening of a flat tube is expanded while the tube remains inserted into a tube hole formed in a header member, thereby bringing the opening into close contact with the tube hole. Methods described in: for example, Japanese Patent Publication Nos. Sho. 59-180295 and Sho. 60-49861, have already been known as manufacturing methods of this type.
FIG. 14 shows a manufacturing method described in Japanese Patent Publication No. Sho. 60-49861. According to this method, a core section 4 is interposed between header members 1 spaced apart from each other by a given distance so as to be mutually oppose. The core section 4 is assembled by alternating arrangement of tubes 2 and corrugated fins 3.
Respective ends of the tubes 2 are inserted into corresponding tube holes 1a formed in the header member 1. Expansion wedges 6 formed on each of jigs 5 disposed on opposite sides of the core section 4 are inserted into openings 2a of the tubes 2, thereby bringing the openings 2a into close contact with the tube holes 1a. 
Under such a manufacturing method, the openings 2a of the tubes 2 are brought into close contact with the tubes holes 1a, thereby preventing falling of the header members 1 and abating a solder running failure, which would otherwise frequently arise during a brazing process in a subsequent step.
Under such a known manufacturing method, a portion of the edge of the opening 2a of the tube 2 expanded by the expansion protrusion 6 becomes collapsed, as shown in FIG. 15, thus frequently inducing formation of a collapsed portion 2b. 
In the event that the tube 2 becomes partially collapsed, coolant circulating through the tube 2 leaks out from the collapsed portion. For this reason, inspection for collapsed portions requires scrupulous attention and a large number of steps.
Considerable research conducted by the present inventor for solving the drawback of the known manufacturing methods shows that, as shown in FIG. 16, a longitudinal side surface 2c of the tube 2 becomes inwardly deformed during transportation of the tube 2, introduction of the tubes 2 into an assembly facility, or assembly of the core section 4 and that, if the expansion protrusion 6 is inserted into the opening 2a in this state, the expansion protrusion 6 comes into collision with the longitudinal side surface 2c,thus inducing formation of the collapsed portion 2b. 
It is also found that, even when the longitudinal side surface 2c becomes deformed, as shown in FIG. 16, spaces 2d remain present in opposite ends of the flat tube 2.
The present invention has been conceived on the basis of the previously-described finding and is aimed at providing an expansion wedge for use with a heat exchanger tube which can readily and thoroughly prevent collapse of an opening of a tube, as well as a structure for mounting a tube to a header member in a heat exchanger manufactured through use of the expansion wedge.
Accordingly, the present invention provides an expansion wedge for use with a heat exchanger tube which increases the cross-sectional width of an opening of a flat tube inserted into a tube hole of a header member through use of an expansion section to be inserted into the opening and which brings the opening into close contact with the tube hole, the expansion wedge comprising: an expansion wedge body on which there is formed the expansion section for expanding the distance between longitudinal side surfaces of the tube when being inserted a predetermined depth into the opening of the tube, and guide protuberances which are protrusively formed on the respective longitudinal sides of the expansion section and which are inserted into the spaces provided on the respective sides of the opening of the tube, thereby guiding the expansion section into the opening.
Further, the present invention provides a structure for mounting a tube to a header member of a heat exchanger, by means of inserting an opening of a flat tube into a tube hole of a header member, wherein either longitudinal side of the opening of the tube is made so as to have a width greater than that of a center portion, and the opening is brought into press-contact with the tube hole of the header member.
In the expansion wedge of the present invention, the guide protuberances formed at the respective longitudinal sides of the expansion section are inserted into the spaces provided on the respective sides of the opening of the tube, thereby guiding the expansion section into the opening.
The expansion section is inserted into the opening, thereby increasing the distance between the longitudinal sides of the opening of the tube. As a result, the opening is brought into close contact with the tube hole.
In the structure for mounting a tube to a header member, either longitudinal side of the opening of the tube is made so as to have a width greater than that of a center portion, and the respective longitudinal sides of the opening are brought into press-contact with the tube hole of the header member.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
Another aspect of the invention resides in a structure for mounting a flat tube to a header member of a heat exchanger, comprising: a tube hole formed in the header member; and an opening of the flat tube being inserted into the tube hole, the opening of the flat tube having longitudinally opposed end sections and a center section which is located between the end sections, wherein the opening of the flat tube is expanded in such a manner that both longitudinally opposed end sections of the opening of the flat tube have opposed sides which have a width greater than any widths of opposed sides of the center portion of the opening of the flat tube, so that at least the opposed sides of the end sections of the opening of the flat tube are brought into press-contact with the header member around the tube hole.